1. Field of the Invention
This invention pertains to processing multiple moving webs, and more particularly to apparatus that sheets a first web into discrete articles and merges the articles with a carrier web.
2. Description of the Prior Art
Numerous products are manufactured from one or more moving webs of flexible materials. To manufacture such products, various types of equipment have been developed to handle the webs. For example, many prior machines overlay two or more webs, which are often laminated to each other. The composite web is usually cut into individual products. U.S. Pat. Nos. 5,803,888 and 6,030,329 are representative of such prior web handling equipment.
It is also well known to capture discrete articles between two webs and to seal the webs to each other around the articles. The webs are then cut to make individual products consisting of the article and the surrounding web material. Examples of prior machines and the products produced by them may be seen in U.S. Pat. Nos. 4,244,158; 4,369,613; 4,601,157; 4,864,802; 5,044,145; 5,357,731; 5,628,165; 5,875,614; and 6,115,999.
In the nine aforementioned patents, the respective articles to be packaged are supplied to the machinery as discrete rigid objects. Suitable mechanisms space the articles at the required distances as they approach the webs and are captured between them.
U.S. Pat. No. 6,018,092 describes a flexible medical product that has an adhesive bandage between two sheets. The adhesive bandage is spaced from the sheets edges, but no description is given as to how the placement of the adhesive bandage on the sheets is accomplished.
The prior equipment for manufacturing individual products works well for their intended uses. Nevertheless, the prior equipment is subject to further refinements.
In accordance with the present invention, a slip cutting system is provided that sheets an infeed web of flexible material into discrete articles and then merges the articles to a carrier web. This is accomplished by apparatus that includes a rotary cutting die having at least one knife blade and at least one friction packing. The slip cutting system may be part of a machine that also cuts the carrier web to manufacture individual products.
The cutting die cooperates with an anvil roller of constant working diameter to form a nip that defines a nip plane. The anvil roller is mounted for rotation at its opposite ends at a fixed location in the machine frame. The cutting die is journaled at its opposite ends in die blocks. The cutting die is generally cylindrical in shape, having a longitudinal axis and a peripheral surface between two cylindrical rails. Protruding above the peripheral surface between the rails is the knife blade, which is parallel to the longitudinal axis. The packing is made from any material that is compatible with the infeed web. The packing is relatively thin, and it is bonded to the cutting die peripheral surface. A leading edge of the packing is adjacent the knife blade. A trailing edge of the packing is spaced circumferentially from the knife blade. If there is more than one knife blade, there is a packing in association with each knife blade. The leading edge of each packing is adjacent a knife blade. The trailing edge of each packing is spaced from the next consecutive knife blade.
The cutting die blocks are retained for sliding in slots in the machine frame such that the center distance between the cutting die and the anvil roller is variable. At a minimum center distance, the anvil roller contacts the cutting die rails.
There is a force mechanism in operative association with the cutting die. According to one aspect of the invention, the force mechanism comprises bearing blocks that are retained for sliding in the same slots as the die blocks. The bearing blocks rotatably support opposite ends of a bearing bar. A set of bearings held on the bearing bar contact the cutting die rails diametrically opposite the anvil roller. A pressure plate is fixed to the machine frame over each slot. A long screw threads through each pressure plate and bears against the associated bearing block. Turning the screws forces the bearing bar bearings against the cutting die rails.
Upstream of the cutting die and anvil roller is an infeed bar that lies across the path of the infeed web. The infeed web is guided into the nip between the cutting die and the anvil roller by the infeed bar. By varying the infeed bar position, the angle at which the infeed web enters the nip can be varied to suit the particular infeed web.
The infeed web is supplied from a roll upstream of the infeed bar. Between the infeed web supply roll and the infeed bar is a drag station. At the drag station, a drag force is imparted to the infeed web that resists downstream motion of the infeed web toward the slip cutting system.
According to one embodiment of the invention, the carrier web consists of top and bottom webs, and the slip cutting system includes an insert station at which the articles are inserted and captured between the top and bottom webs. The insert station is comprised of three guide rods that are parallel to the cutting die longitudinal axis. First and second guide rods are close to the downstream side of the nip. The first and second guide rods are located approximately equidistantly on opposite sides of the nip plane. The third guide rod is located downstream of the first and second guide rods. The top edge of the third guide rod is on the same side of the nip plane as the first guide rod. In machines in which the cutting die is vertically above the anvil roller, the nip plane is horizontal. In that situation, the top edge of the third guide rod is above the nip plane.
The top web is guided around the first guide rod and then passes over the third guide rod. The bottom web is guided around the second guide rod and passes over the third guide rod, between the third guide rod and the top web. Consequently, a triangular shaped space is present between the top and bottom webs, with the space apex being at the third guide rod.
Downstream of the slip cutting system is a drive station. The drive station pulls the top and bottom webs continuously downstream.
In operation, the force mechanism screws are turned to apply a measured amount of force between the bearing bar bearings and the cutting die rails. The same force is applied between the cutting die rails and the anvil roller. The drive station continuously pulls the top and bottom sheets from their respective supply rolls through the insert station. Simultaneously, the cutting die rotates continuously at the same surface speed as the webs speed. The infeed web is drawn into the nip between a cutting die packing and the anvil roller. Friction between the cutting die packing and the infeed web draws the infeed web through the nip, against the drag force imparted to the infeed web at the drag station, for a part of a revolution of the cutting die and anvil roller.
When the trailing edge of the packing has passed the nip, the circumferential space between the packing trailing edge and the knife blade reaches the nip. The previously existing friction force between the packing and the infeed web disappears. That friction force is replaced by a much smaller friction force of the cutting die peripheral surface on the infeed web. The smaller friction force is not sufficient to draw the infeed web against the drag force. Consequently, the infeed web halts its downstream motion. As the cutting die continues to rotate, the knife blade approaches and then sheets the stationary infeed web at the nip with the anvil roller to make a discrete article from the infeed web. Almost instantly, the leading edge of the packing adjacent the knife blade comes into contact with the new leading end of the infeed web at the nip and reestablishes the friction force between the infeed web and the cutting die packing. The infeed web is again drawn through the nip. At the same time, the knife blade pushes the trailing edge of the sheeted article downstream to the insert station. The article enters the triangular space between the top and bottom webs, and it is captured between them. Friction of the two webs on the article propels the three-component composite web in the downstream direction for further processing.
The constantly rotating cutting die draws the infeed web until the packing trailing edge is again at the nip. The infeed web again halts downstream motion while the cutting die circumferential space passes over the infeed web. While the infeed web downstream motion is halted, the continuously moving top and bottom webs continue to propel the previously sheeted article in the downstream direction. The knife blade eventually reaches the nip and again sheets the infeed web and pushes the newly sheeted article downstream. However, the leading edge of the newly sheeted article is spaced from the trailing edge of the previously sheeted article a distance determined by the circumferential space between the packing trailing edge and the knife blade. Accordingly, the sheeted articles are at longitudinally spaced intervals between the top and bottom webs of the composite web. The composite web may be sealed and cut into individual products downstream of the insert station.
The method and apparatus of the invention, using an intermittently applied friction force between an infeed web and a cutting die, thus sheets the infeed web into discrete articles and merges the articles to a carrier web. The articles are spaced apart longitudinally along the carrier web, even though the cutting die continuously rotates at a constant speed.
Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention.